Watched A Discovery of the Witches (sky) first, liked it a lot, so decided to read the books. This is not my usual order. Normally, I read the book first, then watch the film (especially for the classics), or only watch the film, or only read the book. If the book I read first is really good, I often refrain from watching the adaptations, because I like my own imaginary world too much to want to 'contaminate' it with other people's visions. That was the case for me with The Lord of the Rings and Harry Potter (though I've now seen clips since those adaptations came out).
So far, I have read volumes 1 and 2 by Deborah Harkness, reading the 3rd one. At the beginning of ADOB it felt so weird, like reading the best fanfic ever based on my favourite screen characters, so funny. But with every chapter, I entered that world more and more. And while I remember well what is and isn't in the tv series (after a few rewatches), the page and the screen have blended in my mind into one world. The casting was superb, I love them all (with one minor exception), so I 'borrowed' them into the book world. Obviously, there are necessary omissions I wish had been included, and a few changes to the plot which I would not have made, but on the whole, I appreciate how the TV series tackled this vast material. And in awe of Deborah Harkness' genius.
Several people are credited as the writers for different seasons/episodes, including Kate Brooke, Charlene James, and Sarah Dollard. I would really like to get their views on how they go about the page-to-screen transfer.
Anyway, a long-time dream is to sit in a writers' room working on an adaptation of a fiction production... Maybe one day... I have cast the spell. :-)